NAME

URI::GoogleChart - Generate Google Chart URIs

SYNOPSIS

use URI::GoggleChart;
my $chart = URI::GoogleChart->new("line", 300, 100,
    data => [45, 80, 100, 33],
);

DESCRIPTION

This module provide a constructor method for Google Chart URIs. Google will serve back PNG images of charts controlled by the provided parameters when these URI are dereferenced. Normally these URIs will be embedded as <img src='$chart'> tags in HTML documents.

The Google Chart service is described at http://code.google.com/apis/chart/ and these pages also define the API in terms of the parameters these URIs take. This module make it easier to generate URIs that conform to this API as it automatically takes care of data encoding and scaling, as well as hiding most of the cryptic parameter names that the API uses in order to generate shorter URIs.

The following constructor method is provided:

$uri = URI::GoogleChart->new( $type, $width, $height, %opt )

The constructor method's 3 first arguments are mandatory and they define the type of chart to generate and the dimension of the image in pixels. The rest of the arguments are provided as key/value pairs. The return value is an HTTP URI object, which can also be treated as a string.

The $type argument can either be one of the type code documented at the Google Charts page or one of the following more readable aliases:

lines
sparklines
xy-lines

horizontal-stacked-bars
vertical-stacked-bars
horizontal-grouped-bars
vertical-grouped-bars

pie
pie-3d
concentric-pie

venn
scatter-plot
radar
radar-splines
google-o-meter

world
africa
asia
europe
middle_east
south_america
usa

The key/value pairs can either be one of the chXXX codes documented on the Google Chart pages or one of the following:

data => [{ v => [$v1, $v2,...], %opt }, ...]

data => [[$v1, $v2,...], [$v1, $v2,...], ...]

data => [$v1, $v2,...]

data => $v1

The data to be charted is provided as an array of data series. Each series is defined by a hash with the v element being an array of data points in the series. Missing data points should be provided as undef. Other hash elements can be provided to define various properties of the series. These are described below.

As a short hand when you don't need to define other properties besides the data points you can just provide an array of numbers instead of the series hash.

As a short hand when you only have a single data series, you can just provide a single array of numbers, and finally if you only have a single number you can provide it without wrapping it in an array.

The following data series properties can be provided.

The "group" property can be used to group data series together. Series that have the same group value belong to the same group. Values in the same group are scaled based on the minimum and maximum data point provided in that group. Data series without a "group" property belong to the default group.

min => $num

max => $num

Defines the minimum and maximum value for the default group. If not provided the minimum and maximum is calculated from the data points belonging to this group. Chart types that plot relative values make the default minimum 0 so the relative size of the data points stay the same after scaling.

The data points are scaled so that they are plotted relative to the ($min .. $max) range. For example if the ($min .. $max) range is (5 .. 10) then a data point value of 7.5 is plotted in the middle of the chart area.

group => { $name => { min => $min, max => $max }, ...},

Define parameters for named data series groups. Currently you can only set up the minimum and maximum values used for scaling the data points.

encoding => "t"

encoding => "s"

encoding => "e"

Select what kind of data encoding you want to be used. They differ in the resolution they provide and in their readability and verbosity. Resolution matters if you generate big charts. Verbosity matters as some web client might refuse to dereference URLs that are too long.

The "t" encoding is the most readable and verbose. It might consume up to 5 bytes per data point. It provide a resolution of 1/1000.

The "s" encoding is the most compact; only consuming 1 byte per data point. It provide a resolution of 1/62.

The "e" encoding provides the most resolution and it consumes 2 bytes per data point. It provide a resolution of 1/4096.

The default encoding is currently "t"; but expect this to change. The default ought to be automatically selected based on the resolution of the chart and the number of data points provided.

color => $color

color => [$color1, $color2, ...]

Sets the colors to use for charting the data series. The canonical form for $color is hexstrings either of "RRGGBB" or "RRGGBBAA" form. When you use this interface you might also use "RGB" form as well as some comon names like "red", "blue", "green", "white", "black",... which are expanded to the canonical form in the URI.

title => $str

title => { text => $str, color => $color, fontsize => $fontsize }

Sets the title for the chart; optionally changing the color and fontsize used for the title.

margin => $num

margin => { left => $n, right => $n, top => $n, bottom => $n }

Sets the chart margins in pixels. If a single number is provided then all the margins are set to this number of pixels.

SEE ALSO

http://code.google.com/apis/chart/

URI

COPYRIGHT AND LICENSE

Copyright 2009 Gisle Aas.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.